Wind-powered weapons How Ukraine is using balloons to overwhelm Russia’s air defenses

During a drone attack on Russian regions on Monday night, Ukrainian forces deployed a large number of balloons, according to sources in Russia’s Defense Ministry. The sources said it was the first time they had seen Ukraine use them on this scale. They gave no details about the balloons’ intended targets or technical specs, and provided no photos.

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Nothing for certain — we can only speculate. They were likely weather balloons or something similar: helium-filled latex spheres several meters across at ground level that expand as they rise.

Both Ukraine and Russia have used balloons before to overload air defense systems and radar. The logic is simple: every system can track only so many targets at once. An S-300, for instance, can handle about 65 flying objects. And to track them, the system has to switch its radars to active mode, which exposes their position. That, in turn, allows the enemy to chart radar locations and plan flight paths for drones or missiles that slip between those zones.

To throw off air defense systems, the balloons are fitted with metal corner reflectors that distort and enlarge their radar cross-section. These are usually tetrahedrons or octahedrons that bounce radar beams straight back to the transmitter.

They aren’t. With no engines, they drift wherever the wind takes them. That works only if the wind is blowing toward enemy territory — as it was on the night of September 22, when a southwesterly breeze of 12–15 kilometers per hour (about 7–9 miles per hour) carried balloons from northeastern Ukraine toward Tula, Ryazan, and Moscow.

Southwesterly winds tend to predominate across much of that area, which gives Ukraine a built-in advantage when it uses these kinds of air defense decoys.